It may be a trial balloon, or it may be a real movement, but a growing number of Republican lawmakers are now saying they are willing to junk the Grover Norquist pledge they signed to oppose all tax increases if it would help get a deal to avert the “fiscal cliff.”

Sen. Bob Corker (R.,Tenn.) was the latest to publicly distance himself from Norquist’s Americans for Tax Reform advocacy group, speaking Monday on CBS This Morning. “I’m not obligated on the pledge,” said Corker, about to begin his second term. “I made Tennesseans aware – I was just elected – the only thing I’m honoring is the oath I take when I serve, when I’m sworn in this January.”

He joins (at least publicly) Republican Sens. Saxby Chambliss of Georgia and Lindsey Graham of South Carolina, as well as Rep. Peter King of New York.

“I agree with Grover, we shouldn't raise rates, but I think Grover is wrong when it comes to we can't cap deductions and buy down debt,” Graham said on ABC's This Week Sunday. “What do you do with the money? I want to buy down debt and cut rates to create jobs, but I will violate the pledge, long story short, for the good of the country, only if Democrats will do entitlement reform.”

Graham, as are many Republicans, is talking about capping deductions and tax credits for wealthier taxpayers, though he says he does not favor increasing marginal tax rates. Yet event his step runs afoul of Norquist’s Taxpayer Protection Pledge, which does not allow for nuances – a tax increase is a tax increase, no matter how you do it.

This movement is among the most interesting developments in the early phase of negotiations between the parties to agree on a package of revenue increases and spending cuts to avert automatic cuts and the expiration of lower tax rates enacted in 2001 and 2003 – amounting to higher tax bills for millions – due to occur Dec. 31 without a deal.

Yet a key question remains: How willing would GOP lawmakers be to actually vote for a concrete revenue raising proposal? After all, Norquist gets his power from the grassroots; a hard-edged anti-tax stand has benefitted the Republican party politically for several decades, and the party’s base might rebel – even to the point of supporting more ideologically pure candidates in primaries against lawmakers who stray.

Just ask former one-term President George H.W. Bush how much it can hurt to backslide on taxes.

Aaron Blake of The Washington Post’s The Fix blog has a very good analysis of this question here.